1. Field of the Invention
The present invention relates to a lightning ground system testing instrument and more particularly to an attachable lightning ground testing instrument that measures the admittance of electrical circuits without physical contact or breaking the circuits.
2. Description of the Prior Art
Lightning ground systems are used on buildings, towers, and other structures throughout the world. There are basically two types of tests that are employed on these lightning ground systems to assure their integrity and proper performance. One is by performing test measurements on a ground system that has been interrupted and the other is by performing test measurements on a ground system that has not been interrupted. In situations where the ground system is not interrupted there are two normally employed testing methods. One is by physical inspection and the other is generally referred to as the ground megger test. The physical inspection of ground systems has the primary disadvantage of not being able to visually observe many types of electrical and mechanical defects in the ground system. In the ground megger test two stakes are driven into the ground at predetermined positions from the grounding stake. A current is passed from the grounding stake to the furthest stake and a test voltage is measured at the center stake. This method depends upon uniform earth conditions and cannot be used to test ocean grounding systems. In situations where the ground system is interrupted, a testing instrument is normally placed in series with the opened circuit of the ground system. This has the disadvantage of not being certain the ground system is operational after it has been closed following the test. In addition, opening the circuit may introduce errors, especially if circuit resistance is small, as in a ground system.
The present invention overcomes these problems by providing an admittance measuring instrument that is particularly useful for testing lightning ground systems in that it provides reliable test information without interruption of the ground system.